Define nitrogen estimation - kjeldahl''s method, Biology

Assignment Help:

Define Nitrogen Estimation - Kjeldahl's Method?

Nitrogen in the protein is estimated by a method referred to as Kjeldahl's method. Although over a period of time many other methods have emerged for determination of organic nitrogen, this method still remains an old favourite because it is reliable and has very well standardized procedures. The method involves the digestion of the weighed sample with concentrated sulphuric acid, selenium oxide, potassuim sulphate and copper sulphate in a long necked special digestion flask known as kjeldahl's flask. Potassium sulphate increases the boiling point of the mixture. Since the digestion results in fuming of the sulphuric acid, the procedure has to be carried out in a fume hood and the procedure takes several hours. The sample is digested until the solution in the digestion flask becomes clear after which it is transferred to an appropriate volumetric flask (usually 50 or 100 ml flask) and the volume is made up to the mark with distilled water. Aliquots of this sample are used for distillation in the kjeldahl's apparatus and nitrogen in the protein is estimated. Most proteins contains 16% nitrogen. Thus, percent nitrogen content is multiplied by 6.25 to get crude protein content.

1805_Nitrogen Estimation - Kjeldahl’s Method.png

The experiment involves decomposition of ammonium sulphate by a fixed volume of alkali (NaOH). Ammonium sulphate on decomposition releases ammonia which is collected in a flask of boric acid solution Tashiro's indicator. With boric acid ammonia forms a complex 'ammoium borate'. As ammonia is distilled into the boric acid, the Tashiro indicator slowly changes colour from pink to green. This is because the colour of the indicator is pH dependent - it is pink in acidic medium and green in alkaline medium. When the green coloured solution containing the boric-acid-ammonia complex is retitrated against H2SO4, the solution slowly becomes acidic again and the indicator becomes pink. This point when colour changes from green to pink is taken as the end point.


Related Discussions:- Define nitrogen estimation - kjeldahl''s method

Explain the sensory respiratory center - feature of medulla, Explain the Se...

Explain the Sensory Respiratory center - Feature of Medulla Respiratory center: The center for regulating rate and depth of respiration is present in the medulla. Here, nerve i

How this affect blood volume and hematocrit, If a large volume of fluid has...

If a large volume of fluid has shifted from the blood into the peritoneal cavity, how would this affect blood volume and hematocrit?

Explain galactosemia, Galactosemia Inability  of conversion of galactos...

Galactosemia Inability  of conversion of galactose  to glucose results in the accumulation of galactose in  the  blood  -  known  as galactosemia. The biochemical defect usuall

What is mutualism, Q. What is mutualism? The Mutualism is the ecologica...

Q. What is mutualism? The Mutualism is the ecological interaction in which both participants advantage and that is obligatory for their survival. The Mutualism is a harmonio

Cobalt deficiency, Cobalt deficiency The deficiency of cobalt is more ...

Cobalt deficiency The deficiency of cobalt is more commonly seen in ruminants fed on diets deficient in this essential micronutrient. Cobalt is stored only in limited amounts

Excretory organs, classification of excretory organs in helminthes, nermato...

classification of excretory organs in helminthes, nermatodes, annelids, molluscs, arthropods and echinodems

Genetics, Considering a pair of homologous chromosomes containing a gene ha...

Considering a pair of homologous chromosomes containing a gene having two different alleles how many different genotypes can the individual present?

Briefly explain about the chromium, Briefly Explain about the Chromium? ...

Briefly Explain about the Chromium? As you will go through this section, you will realize that compared to other minerals, the essentiality of chromium was recognized very late

Citrate levels would be low in the cytosol, When the ratio of insulin to gl...

When the ratio of insulin to glucagon is >1, which is the following is true with regards to fatty acid synthesis? -malonyl CoA will inhibit carnitine palmitoyl transferase 1

Determine the two different alleles, What is meant by saying that in relati...

What is meant by saying that in relation to a given trait conditioned by a gene with two different alleles the gametes are always "pure"? To say that gametes are pure means tha

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd